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Commit 18bef42c authored by Jean-François Moine's avatar Jean-François Moine Committed by Mauro Carvalho Chehab
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[media] gspca - main: Change the bandwidth estimation of isochronous transfer 



Having:
- a mean image size of 0.375 time the max compressed image size and
- a frame rate of 30 fps for small images or with USB 2.0/3.0
seems more realistic and gives less image freezes.

Signed-off-by: default avatarJean-François Moine <moinejf@free.fr>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 965b37a4

drivers/media/video/gspca/gspca.c

+11 −3
Original line number Diff line number Diff line
@@ -633,13 +633,14 @@ static u32 which_bandwidth(struct gspca_dev *gspca_dev) 
	u32 bandwidth;

	int i;



	/* get the (max) image size */

	i = gspca_dev->curr_mode;

	bandwidth = gspca_dev->cam.cam_mode[i].sizeimage;



	/* if the image is compressed, estimate the mean image size */

	/* if the image is compressed, estimate its mean size */

	if (bandwidth < gspca_dev->cam.cam_mode[i].width *

				gspca_dev->cam.cam_mode[i].height)

		bandwidth /= 3;

		bandwidth = bandwidth * 3 / 8;	/* 0.375 */



	/* estimate the frame rate */

	if (gspca_dev->sd_desc->get_streamparm) {
@@ -649,7 +650,14 @@ static u32 which_bandwidth(struct gspca_dev *gspca_dev) 
		gspca_dev->sd_desc->get_streamparm(gspca_dev, &parm);

		bandwidth *= parm.parm.capture.timeperframe.denominator;

	} else {



		/* don't hope more than 15 fps with USB 1.1 and

		 * image resolution >= 640x480 */

		if (gspca_dev->width >= 640

		 && gspca_dev->dev->speed == USB_SPEED_FULL)

			bandwidth *= 15;		/* 15 fps */

		else

			bandwidth *= 30;		/* 30 fps */

	}



	PDEBUG(D_STREAM, "min bandwidth: %d", bandwidth);